Gear Diff Help

[Cremegg]

Hi All

Im just looking for a little help regarding my gear diff.

Ive been advised to put 3000 oil in but i dont know if this is in watt or Cst?

I opened the diff up and found a smelly black grease in here but no oil? is this normal?

I tested to see if the diff was leakproof with a bit of diff oil but it seems to leak out of where the outdrives are for the CVD's

Is there an alternative to oil in this case, if the diff is not leakproof?

Thanks